Impact of climate change on human health

by: Mahmodul Hasan Shesheir

Climate change poses a fundamental hazard to human health. It has an impact on the physical environment as well as all aspects of natural and human systems, such as social and economic situations and the operation of healthcare systems. It is thus a threat multiplier, eroding and possibly undoing decades of health improvement. As climatic conditions change, weather and climate phenomena such as storms, extreme heat, floods, droughts, and wildfires become more often and intense. These weather and climate hazards have a direct and indirect impact on health, increasing the risk of death, non-communicable diseases, the appearance and spread of infectious diseases, and health emergencies.

Climate change is also having an impact on our health workforce and infrastructure, reducing the capacity to provide universal health coverage (UHC). Climate shocks and developing pressures, such as shifting temperature and precipitation patterns, drought, flooding, and rising sea levels, hurt the environmental and social determinants of physical and mental health. Climate change affects many elements of health, including clean air, water, and soil as well as food systems and livelihoods. Further delays in addressing climate change would raise health risks, erode decades of progress in global health, and violate our collective promises to safeguard the fundamental right to health for all.

Climate change impacts on health

The Intergovernmental Panel on Climate Changes (IPCC) Sixth Assessment Report (AR6) indicated that climate risks are emerging quicker and becoming more severe than previously anticipated, and that adaptation will be increasingly difficult as global temperatures rise. It also demonstrates that 3.6 billion people already live in places highly vulnerable to climate change. Despite contributing minimally to global emissions, low-income countries and small island developing states (SIDS) face the most severe health consequences. In sensitive areas, the death rate from extreme weather events was 15 times greater in the recent decade than in less vulnerable areas.

Climate change has a wide-ranging impact on health, including increased death and illness from extreme weather events such as heatwaves, storms, and floods, disruption of food systems, increases in zoonoses and food-, water-, and vector-borne diseases, and mental health issues. Furthermore, climate change is threatening many of the social determinants of good health, including livelihoods, equality, and access to health care and social support networks. These climate-sensitive health hazards disproportionately affect the most vulnerable and disadvantaged groups, such as women, children, ethnic minorities, poor communities, migrants or displaced people, the elderly, and those with underlying health issues.

Although it is clear that climate change has an influence on human health, correctly estimating the extent and impact of many climate-sensitive health concerns continues to be difficult. However, scientific discoveries are gradually allowing us to ascribe an increase in morbidity and death to global warming, as well as more accurately determining the dangers and magnitude of these health problems. According to WHO estimates, 2 billion people lack access to safe drinking water and 600 million suffer from foodborne infections each year, with children under the age of five accounting for 30% of foodborne deaths. Climate stressors increase the likelihood of disease transmission through water and food. In 2020, 770 million people suffered hunger, primarily in Africa and Asia. Climate change has an impact on food availability, quality, and diversity, increasing the food and nutrition crisis.

Temperature and precipitation fluctuations contribute to the spread of vector-borne diseases. Without preventive measures, mortality from such diseases, which already exceed 700,000 per year, may increase. Climate change causes both immediate mental health concerns, such as anxiety and post-traumatic stress disorder, as well as long-term disorders, as a result of displacement and disturbed social cohesiveness. According to a recent study, human-caused climate change accounts for 37% of heat-related mortality. Heat-related mortality among people over the age of 65 have increased by 70% in the past two decades. In 2020, 98 million more people suffered food insecurity than the 1981-2010 average. The World Health Organization estimates that climate change-related diseases such as malaria and coastal floods will cause 250,000 more fatalities per year by the 2030s.

However, modeling issues remain, particularly in identifying threats such as drought and migration pressures. The climate catastrophe threatens to undermine the last 50 years of gains in development, global health, and poverty reduction, as well as to exacerbate current health disparities between and within communities. It jeopardizes the achievement of UHC in a variety of ways, including by adding to the existing disease load and worsening existing barriers to obtaining health services, frequently at the most critical moments. More than 930 million individuals, or around 12% of the world's population, spend at least 10% of their household budget on health care. With the poorest people mainly uninsured, health shocks and strains already drive approximately 100 million people into poverty each year, with the effects of climate change exacerbating the trend.

Climate change and equity

In the short to medium term, the health effects of climate change will be primarily defined by population susceptibility, resilience to existing rates of climate change, and the extent and pace of adaptation. In the long run, the consequences will be increasingly determined by how much transformational action is made now to decrease emissions and prevent dangerous temperature thresholds and potential irreversible tipping points. While no one is immune to these risks, the people whose health is being harmed the most by the climate crisis are those who contribute the least to its causes and are least able to protect themselves and their families from it: people living in low-income and disadvantaged countries and communities.

Need for rapid action

To avoid catastrophic health consequences and prevent millions of climate change-related fatalities, the world must restrict temperature rise to 1.5 degrees Celsius. Past emissions have already made some level of global temperature rise and other climate impacts unavoidable. Even 1.5°C of global warming is not regarded safe; each additional tenth of a degree of warming will have a significant impact on people's lives and health.

Mahmodul Hasan Shesheir, public health researcher at BRAC James P Grant School of Public Health, Co-author: Mehadi Shawon, Graduate Student at North Dakota State University, USA